Previous studies indicate that delta 9 THC elicits antiandrogenic, and estrogen-like effects in humans and rats. In our laboratories, preliminary results indicate that THC administration in growing male rats evokes altered patterns of somatic and skeletal growth which are similar to those obtained with equivalent doses of estrodial in young male rats; the increased adrenal and decreased seminal vesicle weights of rats receiving THC lend further support to the possibility that THC has estrogen-like effects. High levels of estrogen are believed to have carcinogenic, diabetogenic and thrombogenic effects, and estrogen therapy is contraindicated for individuals with histories of neoplastic, diabetic or hypertensive disorders. Since the possible estrogen-like action of marihuana may effect several clinical conditions, chronic use of marihuana may be of significance in persons for whom estrogens are contraindicated. Since THC crosses the placental barrier, the possibility of synergism between THC and estrogen is of especial interest since estrogen mimics prenatal androgen at the critical stages of sexual differentiation. We wish to examine the estrogen-like effect of THC in female rats, and to explore the possibility of synergism between THC and estrogen in these animals. The maintenance of secondary sex characteristics and somatic and skeletal growth of ovariectomized rats maintained on either estrodial benzoate or THC alone, or on both estrodial benzoate and THC will be compared in operated and unoperated female rats. Uterine weight assay will be evaluated as a bioassay for THC. The effect of THC on blood glucose and lipoprotein levels as well as reproductive behavior of ovariectomized rats will be examined.